A. Field of the Invention
It is well known in the art that most conventional high intensity discharge (HID) lamps cannot be instantly turned on to full brightness and intensity. Likewise, such lamps cannot be turned off and then quickly turned on again to full intensity. They generally require a re-strike or warm-up period of time.
Incandescent lamps do not have the re-strike problem. Special types of arc lamps, called instant re-strike arc lamps, are available but they are very expensive. Additionally, instant re-strike arc lamps do turn on quickly after they have been turned off, however, if shut off for more than a few minutes, they may re-light at a different temperature or color than what is preferred or needed.
HID lamps are desirable for many uses because the type (color, intensity) of output and the economy of such lamps. This is specially true for lighting of large areas where the light must be controlled and concentrated for projection over substantial distances.
The re-strike problem, as previously stated, is widely recognized in the art. Attempts have been made to deal with that situation and allow relatively quick on/off control. One such attempt utilizes a dimming circuitry to reduce the current to the arc lamp. This reduces the brightness or intensity but does not extinguish the light so complete darkness cannot be achieved.
Attempts have also been made to leave the light at full power but to block the light. Primary problems with this approach include the heat buildup that occurs when blocking such high intensity lights, and difficulty in sealing off the light to achieve total blockage of light.
Symmetrical reflectors (hereafter also sometimes called bowl-shaped or spherical reflectors) produced from surfaces of revolution are an economical, effective choice for high efficiency, controlled concentrated beams over long distances. Trough reflectors or other non-symmetrical shapes are sometimes used for these purposes, but most times they utilize housings, and several support or enclosure pieces for structural support. Their make-up is therefore more complex and expensive than symmetrical reflectors, which can both perform reflecting functions and support such things as a lens without additional framework or housings.
Substantial difficulties face one who wishes to attempt to simply block light from such a fixture. No method or structure is known to adequately do so.
Some of the problems are:
1. Strength problems--symmetrical reflectors are generally made of relatively thin metal such as aluminum and cannot bear too much weight or stress.
2. Light sealing--it is difficult to place a block that can be moved in front of the lamp and effectively seal all light emanating from the lamp when on full power.
3. Heat--once closed or even partially closed, the heat buildup is a concern for the structural integrity of the reflector and mounting components, as well as the structure blocking the lamp and the lamp itself. Any significant rise in temperature at or near the lamp may affect performance or even the ability for operation of the lamp.
4. Weight--along with the strength problem, the additional weight of structure to block the lamp is a concern.
5. Complexity--because most lighting applications use numerous fixtures, cost is a high concern as well as the complexity of the structure for reliability of operation and longevity.
Other concerns facing one who desires to achieve an on/off fixture include the flexibility to have some sort of light control in the form of spill or glare control and the ability to produce special effects, for example, different color outputs, strobe affect, and other theatrical type lighting effects.
There is therefore a real need in the art for a lighting fixture that uses a spherical reflector and an HID lamp that has the re-strike problem, but which can quickly have its light output completely blocked or unblocked.
It is therefore a principle object of the present invention to provide a lighting fixture with a controllable light block that solves or improves over the problems and deficiencies in the art.
Another object of the present invention is to provide an apparatus as above described which can completely block light output from the fixture on command.
Another object of the present invention is to allow block off of light from the fixture immediately on command.
Another object of the present invention is to allow light from the fixture to be blocked for indefinite continuous periods of time without danger of detrimental heat buildup.
Another object of the present invention is to provide an apparatus having a minimum number of moving parts and which is not complex in structure.
Another object of the present invention is to have the flexibility for special light control and special lighting effects.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.